Information and help on glass fusing, stained glass, kiln forming, acid etching, sandblasting and other areas of working with glass.

Wednesday, 10 February 2016

Hand Finishing to a Flat Edge.

Hand finishing an edge does not require
expensive electrical tools, although they do make the process quicker. This is a note on how to get good-looking
edges without expensive equipment. Only a few materials are required.

·A thick sheet of
float glass for the grinding plate

·Aluminium oxide or
silicon carbide grit in approximately 80, 180, 400, and 600 grits to act as the
abrasive.

·Wet and dry
sandpaper of approximately 1200 and 2400 grits

·Paint pens (white
and gold work well)

·Paper towels for
drying

·Water for rinsing

·Large bucket or
basin to collect the rinsing water

The thick flat float glass acts as the
grinding plate. It is flat and smooth,
making the grinding and polishing flat.

If you have a lot of glass to take off to get a
straight edge use 60 or 80 grit. If
there is not much to take off, start with 120 or 180 grit. There is no need to make deep scratches on
the edge that will take time to eliminate, if a finer grit will do the job.

Put 80 (or finer) grit aluminium oxide or
silicon carbide on the glass grinding plate and make slurry with water.

Slurry mixed and the circular motions of grinding can be seenphoto: hisglassworks

Move the edge firmly in circular or figure of eight motion over the grinding plate until flat. If the slurry becomes pasty, add
more water as you do not want a thick grinding mix. Maintain the same angle of
the glass piece to the grinding plate at all times so you have only one plane
of glass to take to a polish.

When the edge is flat, clean and dry the glass,
and especially the ground surface to remove all traces of the coarser grit. Set the piece aside to dry.

While the piece is drying, clean off the
grinding plate. Scrape off the slurry into a pot set aside for that grit for
further use, or into newspaper or other temporary container and then into a
waste bin, not the drains. It is a heavy
material and will block drains. Rinse the plate off in a basin of water to
ensure there are no coarse grains on the glass.
The residue will settle to the bottom and you can decant the water off
once it clears. These grits are not very expensive so repeated use is not
essential, just economical.

The next step is to paint the now dry glass edge
with a white paint pen. This will allow
you to see when you are ready for the next step, by the disappearance of the
paint from the scratches. Of course, if
you are grinding a white or other pale glass, a gold paint pen will be better
to see those scratches.

While the paint is drying, make a slurry of the
next finest grit. Then begin grinding. The first element in each grinding stage
is to give an arris to the edge of the glass.
This prevents chipping the sharp edges.

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When the white paint is gone from the
edge, you can progress to the next grit.

At each stage of grinding you can reduce
the grit size by half (double the number). This is the generally accepted
reduction of grit size to make the removal of the scratches of the previous
grit least time consuming. You can reduce the grit size by more than half if
you want. Most often reducing grit by large amounts means more time is spent at
each stage. Experience will show you how
much you can reduce the grit sizes beyond the accepted intervals.

Stopping at 600 or 800 grit will enable an edge to be fire polished with ease and minimum heat.

At each stage you need to clean the glass
and grinding plate as for the first change of the grit size. This repeated
cleaning usually means that the artist either has separate grinding plates for
each grit, or the grinding is saved up until there are a few pieces that need
the same treatment.

A piece of wet and dry sandpaper fixed to a glass plate

After 800 grit, you may wish to progress
to wet and dry sandpaper for the finer polishing, using 1200, 2400 and, if you
want. 6000 grit. Fix
the paper to a glass plate.Often,
simply folding two edges under the glass will be enough.Add water and proceed as for loose grit.Hand finishing to this level will eliminate
the need for fire polishing.

Of course, for smaller areas, you may wish to use diamond hand pads. The need to use water and rinse between grits still applies. The diamond hand pads are usually most suitable for short straight edges. The longer ones need the kind of treatment outlined above.

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